In recent years, following the spread of counters, inkjet printers are widely utilized for printing on paper, films, cloths, etc. in not only offices but also households.
The inkjet recording method includes a mode of applying a pressure by a piezoelectric element to discharge droplets; a mode of generating bubbles in an ink by heat to discharge droplets; a mode of using ultrasonic wave; and a mode of sucking and discharging droplets by electrostatic force. As ink compositions for such inkjet recording, aqueous inks, oil based inks, or solid (melt type) inks are used. Of these inks, aqueous inks are the main current from the standpoints of manufacture, handling, smell, safety, etc.
With respect to coloring agents that are used in these inkjet recording inks, there are requirements that they have high solubility in solvent; that they can undergo high-density recording; that they have good hu; that they have excellent fastness to light, heat, air, water, and chemicals; that they have good fixation to an image receiving material and hardly cause bleeding; that they have excellent preservability as an ink; that they have no toxicity; that they have high purity; and that they can be cheaply obtained. However, it is extremely difficult to seek coloring agents that can meet these requirements at high levels. Though various inkjet dyes and pigments have already been proposed and actually used, it is the present state that coloring agents that can meet all of the requirements have not yet been discovered. According to the conventionally well known dyes and pigments to which color index (C.I.) numbers are assigned, it is difficult to reconcile hue and fastness required for inkjet recording inks. Also, recently, technological development on inkjet printers targeting photographic image quality is eagerly carried out. For the sake of satisfactorily printing portraits, there have been developed kinds of machines mounted with a dark yellow ink comprising a yellow ink mixed with a pigment having absorption in a cyan or magenta region, in addition to conventional ones mounted with a yellow ink (for example, a PM-950C printer of Seiko Epson Corporation).
The present inventors proceeded with development of inkjet inks using dyes. However, it has been noted that there is a problem such that a dark yellow ink having excellent durability to ozone is hardly obtained.
As background arts, there are JP-A-2002-060664, JP-A-2002-105366, JP-A-2002-105367, JP-A-2002-105358, JP-A-2002-138224 and the like.